How does Java use number lists and arithmetic operations to get target numbers
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Given a list of numbers and a target number, write a program to determine whether the target number can be calculated by applying the "+-* /" operation to the number list? You can assume that () will be added automatically if necessary. An operator should be placed between every two consecutive numbers. So every number must be used.
For example, given {1, 2, 2, 3, 4, and 21, return true. Because (1 / 2) * (3 / 4) = 21
Java solution
This is a partitioning problem that can be solved by using depth-first search.
Public boolean isReachable (ArrayList list, int target) {if (list = = null | | list.size () = = 0) return false; int i = 0; int j = list.size ()-1; ArrayList results = getResults (list, I, j); for (int num: results) {if (num = = target) {return true;} return false } public ArrayList getResults (ArrayList list, int left, int right) {ArrayList result = new ArrayList (); if (left > right) {return result;} else if (left = = right) {result.add (list.get (left)); return result;} for (int I = left; I < right List +) {ArrayList result1 = getResults (list, left, I); ArrayList result2 = getResults (list, I + 1, right); for (int x: result1) {for (int y: result2) {result.add (x + y); result.add (x-y); result.add (x * y) If (y! = 0) result.add (x / y);} return result;} above is all the content of the article "how Java uses number lists and arithmetic operations to get target numbers". Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.
